1,687 research outputs found
The Structural Finite Element Model of the C-5A
A substructured NASTRAN model of the C-5A was analyzed for several different load conditions. The size of the model and the number of load cases used presented special problems in computer file and space management. This resulted in revisions to the in-house NASTRAN code. Despite the problems encountered the analyses were completed with excellent results
Flight control electronics reliability/maintenance study
Collection and analysis of data are reported that concern the reliability and maintenance experience of flight control system electronics currently in use on passenger carrying jet aircraft. Two airlines B-747 airplane fleets were analyzed to assess the component reliability, system functional reliability, and achieved availability of the CAT II configuration flight control system. Also assessed were the costs generated by this system in the categories of spare equipment, schedule irregularity, and line and shop maintenance. The results indicate that although there is a marked difference in the geographic location and route pattern between the airlines studied, there is a close similarity in the reliability and the maintenance costs associated with the flight control electronics
Solution of the Nonāhomogeneous Helmholtz Equation for Optical Gratings with Perfectly Conducting Boundaries
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/113718/1/sapm1966451383.pd
The Effects of Fish Trap Mesh Size on Reef Fish Catch off Southeastern Florida
Catch and mesh selectivity of wire-meshed fish traps were tested for eleven different mesh sizes ranging from 13 X 13 mm (0.5 x 0.5") to 76 x 152 mm (3 X 6"). A total of 1,810 fish (757 kg) representing 85 species and 28 families were captured during 330 trap hauls off southeastern Florida from December 1986 to July 1988. Mesh size significantly affected catches. The 1.5" hexagonal mesh caught the most fish by number, weight, and value. Catches tended to decline as meshes got smaller or larger. Individual fish size increased with larger meshes. Laboratory mesh retention experiments showed relationships between mesh shape and size and individual retention for snapper (Lutjanidae), grouper (Serranidae), jack (Carangidae), porgy (Sparidae), and surgeonfish (Acanthuridae). These relationships may be used to predict the effect of mesh sizes on catch rates. Because mesh size and shape greatly influenced catchability, regulating mesh size may provide a useful basis for managing the commercial trap fishery
Phonon Density of States and Anharmonicity of UO2
Phonon density of states (PDOS) measurements have been performed on
polycrystalline UO2 at 295 and 1200 K using time-of-flight inelastic neutron
scattering to investigate the impact of anharmonicity on the vibrational
spectra and to benchmark ab initio PDOS simulations performed on this strongly
correlated Mott-insulator. Time-of-flight PDOS measurements include anharmonic
linewidth broadening inherently and the factor of ~ 7 enhancement of the oxygen
spectrum relative to the uranium component by the neutron weighting increases
sensitivity to the oxygen-dominated optical phonon modes. The first-principles
simulations of quasi-harmonic PDOS spectra were neutron-weighted and
anharmonicity was introduced in an approximate way by convolution with
wavevector-weighted averages over our previously measured phonon linewidths for
UO2 that are provided in numerical form. Comparisons between the PDOS
measurements and the simulations show reasonable agreement overall, but they
also reveal important areas of disagreement for both high and low temperatures.
The discrepancies stem largely from an ~ 10 meV compression in the overall
bandwidth (energy range) of the oxygen-dominated optical phonons in the
simulations. A similar linewidth-convoluted comparison performed with the PDOS
spectrum of Dolling et al. obtained by shell-model fitting to their historical
phonon dispersion measurements shows excellent agreement with the
time-of-flight PDOS measurements reported here. In contrast, we show by
comparisons of spectra in linewidth-convoluted form that recent
first-principles simulations for UO2 fail to account for the PDOS spectrum
determined from the measurements of Dolling et al. These results demonstrate
PDOS measurements to be stringent tests for ab initio simulations of phonon
physics in UO2 and they indicate further the need for advances in theory to
address lattice dynamics of UO2.Comment: Text slightly modified, results unchange
Effective control of chronic c-herpesvirus infection by unconventional MHC class Iaāindependent CD8 T cells
Effective Control of Chronic Ī³-Herpesvirus Infection by Unconventional MHC Class IaāIndependent CD8 T Cells
Control of virus infection is mediated in part by major histocompatibility complex (MHC) Class Ia presentation of viral peptides to conventional CD8 T cells. Although important, the absolute requirement for MHC Class Iaādependent CD8 T cells for control of chronic virus infection has not been formally demonstrated. We show here that mice lacking MHC Class Ia molecules (K(bā/ā)xD(bā/ā) mice) effectively control chronic Ī³-herpesvirus 68 (Ī³HV68) infection via a robust expansion of Ī²(2)-microglobulin (Ī²(2)-m)-dependent, but CD1d-independent, unconventional CD8 T cells. These unconventional CD8 T cells expressed: (1) CD8Ī±Ī² and CD3, (2) cell surface molecules associated with conventional effector/memory CD8 T cells, (3) TCRĪ±Ī² with a significant VĪ²4, VĪ²3, and VĪ²10 bias, and (4) the key effector cytokine interferon-Ī³ (IFNĪ³). Unconventional CD8 T cells utilized a diverse TCR repertoire, and CDR3 analysis suggests that some of that repertoire may be utilized even in the presence of conventional CD8 T cells. This is the first demonstration to our knowledge that Ī²(2)-mādependent, but Class Iaāindependent, unconventional CD8 T cells can efficiently control chronic virus infection, implicating a role for Ī²(2)-nādependent non-classical MHC molecules in control of chronic viral infection. We speculate that similar unconventional CD8 T cells may be able to control of other chronic viral infections, especially when viruses evade immunity by inhibiting generation of Class Iaārestricted T cells
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